Abstract
Betaine is an important osmoprotectant, and synthesized by many plants in response to abiotic stresses. Almost all known biosynthetic pathways of betaine are two-step oxidations of choline, recently a novel biosynthetic pathway of betaine from glycine, catalyzed by two N-methyltransferase enzymes, was found in a halotolerant cyanobacterium Aphanothece halophytica. Recent studies suggest that for the accumulation of large amount of betaine, supply of precursors such as choline, ethanolamine, and serine as well as choline transport across chloroplast envelop are important. Here, the potential role of serine supply for betaine synthesis was examined in Arabidopsis plants. Arabidopsis plants expressing two N-methyltransferase genes accumulated betaine to a high level in roots, stems, leaves, and flowers, and improved the seed yield under stress conditions. Effects of precursor supply on the accumulation of betaine were examined and their results will be presented.
